1. Field of the Invention
The present invention relates to an apparatus of heating conductors.
2. Description of Related Art
In a system of producing semiconductors used for dry process or plasma coating in semiconductor production, it has been used halogen-based plasma such as F, Cl or the like having high reactivity for etching or cleaning. It is thus required, for a member equipped to such semiconductor production system, high corrosion resistance, so that it has been generally used a member of an anti-corrosive metal such as aluminum with alumite treatment, HASTELLOY or the like or a ceramic material. Especially, it is necessary high corrosion resistance and low particle generation properties for an electrostatic chuck or heater member supporting and fixing an Si wafer, so that it has been used a high corrosion resistant ceramic member such as aluminum nitride, alumina, sapphire or the like. As these materials are used for a long time, they are gradually corroded to induce particle generation, so that it has been demanded a material whose corrosion resistance is further improved. For attending such demands, it is studied to use, as the material, magnesia, spinel (MgAl2O4) or a composite material thereof whose corrosion resistance is higher than that of alumina (For example, Patent document 1; U.S. Pat. No. 3,559,426B).
It is further known a ceramic heater used for heating wafers. In such ceramic heaters, temperature uniformity of the heater is required for heating the wafer uniformly. For example, according to the disclosure of Patent Document 2 (Patent Publication H08-073280A), a heat resistance is embedded in an aluminum nitride based ceramic plate to which an aluminum nitride based shaft is bonded to provide a ceramic heater. According to the descriptions of Patent document 3 (Patent Publication No. 2003-288975A), in a ceramic heater with a shaft, a content of metal carbide in a heat resistance is lowered to reduce the deviation of the carbide content in the heat resistance depending on the positions, so that the temperature distribution on its heating face is reduced.
In the case that a semiconductor wafer is mounted on a susceptor to form a film, it is required uniformity of film thickness particularly in an outer peripheral portion of the semiconductor wafer. As a member for supporting and further heating an Si wafer in a system for producing semiconductors, it has been widely used a ceramic heater made of AlN (aluminum nitride) as described above as an existing art.
Further, as a plasma etching apparatus, for example, it is known the following: it is set, in a chamber for vacuum treatment, a lower electrode functioning as a mounting table for mounting a substrate and an upper electrode provided so as to oppose the lower electrode, and radio frequency power is supplied to the lower electrode to generate plasma of a treating gas. Further, in the plasma etching apparatus of such construction, it is disclosed a construction of providing a focus ring surrounding an outer periphery of the substrate on the lower electrode for improving uniformity in a plane of treatment of the substrate (Patent document 4, Japanese Patent Publication No. 2011-071464A: Patent document 5, Japanese Patent Publication No. 2011-108816A: Patent document 6, Japanese Patent Publication No. 2004-311837A). It is further known that an induction heat generator is provided inside of the focus ring and that the focus ring is heated by induction heating by magnetic field generated by an induction coil provided in a vacuum treatment chamber.